Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Process for Incorporating Whey Proteins into Foodstuffs
The present invention is concerned with the incorporation of
whey proteins into foodstuffs. In particular, the invention
relates to a process for preparing a whey protein-stabilized
fatty emulsion, the thus obtainable whey protein-stabilized
fatty emulsion, a process for incorporating whey proteins
into a foodstuff using said emulsion or an acidified solution
of whey proteins, and the foodstuff thus obtainable.
In the field of the manufacture of food, several attempts
have been made to introduce larger amounts of whey proteins,
for example to replace costly casein proteins and utilize
wasted but rich whey proteins, without a resulting gumminess
(texture effect). With respect to the example of process
cheese, it has been practically impossible to incorporate
larger amounts of whey proteins over a weight ratio of whey
protein to casein of about 10:90. The higher the amount of
whey proteins, the gummier and softer is the resultant
cheese.
The following documents, the disclosure of which is
incorporated herein by reference, represent technological
background material on whey proteins, their properties and
usage in foods:
Kinsella, J.E.; Whitehead, D.M. (1989): Proteins in whey:
Chemical, physical, and structural properties. Advances in
Food and Nutrition Research, 33, 343-438
Konrad, G.; Lieske, B. (1994): Gezielte thermische
Denaturierung - ein~alternativer Weg zu funktionellerem
Molkenprotein. Deutsche Milchwirtschaft, 45, 1130-1134
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Lupano, C. (1994): Effect of heat treatments in very acidic
conditions on whey protein isolate properties. Journal of
Dairy Science, 77, 2191-2198
Patocka, G.; Drathen, M.; Jelen, P. (1987): Heat stability of
isolated whey protein fractions in highly acidic condtions.
Milchwissenschaft, 42, 700-705
Shimizu, M.; Saito, M.; Yamauchi, K. (1985): Emulsifying and
structrual properties of (3-lactoglobulin at different pFis.
Agricultural and Biological Chemistry, 49, 189-194
Strandholm, J.J.; Prochnow, R.R.; Miller, M.S.; Woodford,
L.E.; Naunaber, S.M. (1989): Method for controlling melting
properties of process cheese. Patent US 4 885 183
Swartz, M.L. (1988): Beverage cloud based on a whey protein-
stabilized lipid. Patent US 4 790 998
Yamauchi, K.; Shimizu, M.; Kamiya, T. (1980): Emulsifying
properties of whey protein. Journal of Food Science, 45,
1237-1242
As regards the structural and textural properties of foods,
one possibility to increase the firmness thereof would be the
polymerization of the proteins by an enzyme, namely a
transglutaminase. However, transglutaminases predominantly
polymerize caseins, whereas their reactivity towards whey
proteins is very low or even absent. Thus, the effect of
enzymatic treatment on whey protein-enriched food
compositions is considerably low.
The following documents represent technological background
material on transglutaminases, their effect on proteins and
usage in foods:
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Aboumahmoud, R.; Savello, P. (1990): Cross-linking of whey
proteins by transglutaminase. Journal of Dairy Science 73,
256-263
Budolfsen, G.; Nielsen, P.M. (1999): Method for production of
an acidified edible gel on milk basis. Patent US 5 866 180
Chanyongvorakul, Y.; Matsumara, Y.; Sawa, A.; Nio, N.; Mori,
T. (1997): Polmyerization of (3-lactoglobulin and bovine serum
albumin at oil-water interfaces in emulsions by
transglutaminase. Food Hydrocolloids 11, 449-455
Faergemand, M.; Murray; B.S.; Dickinson, E. (1997): Cross-
linking of milk proteins at the oil-water interface. Journal
of Agricultural and Food Chemistry 45, 2514-2519
Faergemand, M.; Otte, J.; Qvist, K.B. (1997): Enzymatic
cross-linking of whey proteins by a Ca2+-independent
microbial transglutaminase from Streptomyces Iydicus. Food
Hydrocolloids 11, 19-25
Feargemand, M.; Otte, J.; Qvist, K.B. (1997): Emulsifying
properties of milk proteins cross-linked with microbial
transglutaminase. International Dairy Journal 8, 715-723
Kuraishi, T.; Sakamoto, J.; Soeda, T. (1996): Production of
cheese using transglutaminase. Patent Application EP 0 711
504 (JP 81-73032 A2)
Soeda, T. (1999): Cheese whey protein having improved
texture, process for producing the same and use thereof.
Patent Application EP 0 966 887
Traore, F.; Meunier, J.C. (1992): Cross-linking activity of
placental FXIIIa on whey proteins and caseins. Journal of
Agricultural and Food Chemistry 40, 399-402
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Tsukasaki, F.; Minagawa, E.; Mikami, T.; Nonaka, M.; Motoki,
M. (1990): Preparation of cheese food. Patent JP 21-31537 A2
Yamamoto, Y. (1996): Rheology of milk protein gels and
protein-stabilized emulsions cross-linked by
transglutaminase. Journal of Agricultural and Food Chemistry
44, 1371-1377
In view of the above, the present inventors thoroughly
studied the properties of aqueous solutions of whey proteins
and conceived new ways to modify such proteins, thus
providing a solution to the problems of the prior art as
outlined above.
Accordingly, in a first aspect, the present invention
provides a process for preparing a whey protein-stabilized
fatty emulsion, comprising the steps of
- acidifying an aqueous solution of one or more whey
proteins below their isoelectric pH,
- blending and homogenizing the acidified solution of whey
proteins with one or more fats to form a whey protein-
stabilized fatty emulsion, and
- heat-treating said whey protein-stabilized fatty
emulsion at a temperature of more than 80 °C.
Potential sources for the whey proteins referred to herein
are whey protein concentrates (WPC) and whey protein isolates
(WPI), either as reconstituted WPC and/or WPI powders or
preferably as liquid concentrates such as ultrafiltrated
whey. Likewise, normal whey powder may represent a source for
the whey proteins referred to in this description. The whey
can be rennet whey or acid whey. Microfiltration permeate
obtained by using, e.g., a 0.1 Nm membrane, which permeate
contains the native whey proteins, and the ultrafiltrated
concentrate thereof may also be used. A combination of one or
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more whey protein sources may be utilized to provide whey
proteins in the present invention.
The whey proteins initially used in the present invention may
be native or denatured whey proteins, with preference given
to predominantly native whey proteins. However, particulate
and highly denatured whey proteins also exhibit very good
effects in the present invention.
The protein content in the aqueous solution of one or more
whey proteins is preferably at least 4 ~ by weight (with
total solids being, for example, about 10 ~ or more) to reach
the desired whey protein content in the final food products.
The maximum whey protein content is preferably about 20 ~ by
weight. More preferably, the whey protein content of the
aqueous solution is in the range of 8 to 12 ~ by weight
(preferably 12 to 20 ~ total solids).
In the first step of the process for preparing a whey
protein-stabilized fatty emulsion, the aqueous solution of
one or more whey proteins as outlined above is acidified
below the isoelectric pH of the whey proteins contained in
said solution. For the purpose of acidifying the whey protein
solution, any acid may be used that is not objectionable to
the intended application and use of the final whey protein-
stabilized fatty emulsion. Specifically, any food grade acid
such as lactic, citric, phosphoric or hydrochloric acid and
any acidulant such as glucono-b-lactone or vinegar may be
used, alone or in combination of two or more thereof. The
preferred acid is 90 ~ lactic acid. Optionally, it is
possible to employ a lactic acid producing bacterial culture
in the presence of a suitable sugar such as glucose or
lactose, optionally in combination with one or more of the
acids mentioned before. In general, the concentration of the
acids) and the temperature used during acidification are
adjusted such that no detrimental effects are induced. For
example, if there are caseins present in the solution, it may
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be necessary to adjust the initial concentration of the
acids) and the temperature during acidification in such a
way that no coagulation (flocculation) of caseins is induced.
Similarly, too high (e.g. >65 °C) temperatures may induce a
whey protein coagulation if the whey proteins are in the
native state or not fully denatured. Accordingly, room
(ambient) temperature represents a preferred temperature for
a practical application.
The pH accomplished in the acidification step is preferably
considerably below the isoelectric point of the whey proteins
comprised in the aqueous solution. Thus, the pH reached is
preferably in the range of 4.5 to 2.5, more preferably 4.0 to
3.5. As a reference, the isoelectric points of major whey
proteins are: -5.1 (~3-lactoglobulin); 4.2-4.5 (oC-
lactalbumin); 4.7-4.9 (bovine serum albumin) and 6.3-7.0
(immunoglobulin G1).
In the acidification step, the aqueous solution of the whey
proteins is preferably agitated when adding the acid in order
to avoid local peak concentrations of the acid. Although it
is also possible to add the aqueous solution of whey proteins
to an aqueous solution of the acid(s), this may not be the
preferred way of acidification due to potential detrimental
peak acid concentrations. Preferably, the whey protein
solution after addition of the acid is allowed to stand or is
agitated until an equilibrium state is reached, for example,
for one or more minutes, preferable about 10 to 30 minutes.
In the second step of the process for preparing a whey
protein-stabilized fatty emulsion, the acidified solution of
whey proteins is blended and homogenized with one or more
fats. In this step, any fat may be used which is not
objectionable to the desired application of the resulting
fatty emulsion. The preferred fat is milk fat, e.g. in the
form of cream, plastic cream and more preferably butter or
anhydrous butter fat. However, other sources for fats may be
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used, especially vegetable fats and oils, or animal fat, such
as beef tallow,. depending on the application of the whey
protein-stabilized fatty emulsion. A combination of two or
more fats may be used. The one or more fats are used in an
amount such that the ratio of whey protein to fat in the
resulting fatty emulsion is in the range of preferably 3:1 to
1:5 (the total fat content in the fatty emulsion being
preferably in the range of 3 to 30 ~ by weight), more
preferably 2:1 to 1:2.
The blending of the acidified solution of whey proteins with
one or more fats is followed by a homogenization, i.e. a
shear treatment. Blending and homogenizing the two
components, i.e. acidified whey protein solution and fats,
may be a combination of one or more steps. For example, the
components may first be blended and subsequently subjected to
a shear treatment, or blending may be effected simultaneously
in the homogenization, for example by introducing the
components into a homogenizer and starting the device.
Preferably, blending and homogenizing is carried out in a
single apparatus for economic reasons and effectiveness. The
blending and homogenizing step may be carried out using a
conventional homogenizer and is preferably carried out at a
temperature of from 50 to 70 °C and a pressure of from 100 to
300 bar, depending on the fat content (lower pressures may be
more suitable at higher fat levels). In general, the
homogenization can be conducted at a temperature and pressure
and for a period which are conventional in this art.
It is assumed that the resulting whey protein-stabilized
fatty emulsion is of the oil-in-water emulsion type. However,
this assumption should not be construed as restricting the
scope of the present invention, and other structures such as
water-in-oil or bicontinuous structures may be contemplated,
depending on the components and amounts used thereof.
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The blending and homogenizing step is followed by a heat
treatment at a temperature of 80 °C or more, and optionally
at an elevated pressure. The preferred temperature range for
the heat treatment is 80 to 95 °C, and the preferred holding
time is in the range of 1 to 10 minutes, for example a heat
treatment condition of a temperature of 85 °C and a holding
time of 5 minutes. It is assumed that the subsequent heat
treatment should modify the topography of the already changed
whey proteins (due to the acidification below their
isoelectric pH) to make them even more functional, for
example in replacing casein in casein-containing foodstuffs.
Following the blending/homogenization or the heat treatment,
the whey protein-stabilized fatty emulsion may be cooled
(e. g., to room temperature) or directly used in the hot state
in the desired application such as outlined below.
The whey protein-stabilized fatty emulsion obtainable by the
process of the present invention preferably has a fat content
in the range of from 3 to 30 '~ by weight and a whey protein
content in the range of from 5 to 15 ~ by weight. In a
preferred embodiment, an emulsion made in accordance with the
process of the invention (e.g., by mixing WPC and butter) has
20 to 25 ~ total solids, 5 to 10 $ fat, 8 to 12 $ protein and
3 to 5 ~ sugars, based on the total weight of the emulsion
(the presence of additional components such as sugars may
result from the whey protein source such as WPC or the
deliberate addition of further components).
The whey protein-stabilized fatty emulsion obtainable by the
above process represents another aspect of the present
invention.
The protein-stabilized fatty emulsion of the invention may be
used for incorporating whey proteins into a foodstuff. Thus,
in another aspect the present invention provides a process
for incorporating whey protein into a foodstuff comprising
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the steps of blending the whey protein-stabilized fatty
emulsion obtainable by the above process of the invention
with a foodstuff base to form a foodstuff. In an alternative
embodiment, the process for incorporating whey proteins into
a foodstuff comprises the steps of acidifying an aqueous
solution of one or more whey proteins below their isoelectric
pH, heat-treating the acidified solution at a temperature of
more than 80 °C and blending the acidified and heat-treated
solution with a foodstuff base to form a foodstuff. In this
alternative embodiment, the aspects, conditions and
properties of acidifying an aqueous solution of one or more
whey proteins below their isoelectric pH and heat-treating
the acidified solution are as defined above having regard to
the process for preparing a whey protein-stabilized fatty
emulsion.
The foodstuff base may be any dairy or non-dairy based
foodstuff base. In fact, the present inventors have found
that using a specifically acidified and heat-treated whey
protein solution or whey protein fatty emulsion provides a
means for using higher amounts of whey proteins, or to
incorporate more whey proteins, into other food systems.
Preferably, the foodstuff base is a dairy based foodstuff
base and more preferably a casein-containing foodstuff base.
Moreover, the foodstuff base can be foodstuff base containing
meat proteins. Specific examples of the foodstuff base are
bases for cream cheese, process cheese, natural cheese and
mayonnaise, as well as process meat products.
The conditions for blending the fatty emulsion and/or the
acidified and heat-treated whey protein solution and the
foodstuff base are those normally found in the manufacture
(blending of raw materials) of foodstuffs, for example
process cheese, cream cheese or natural cheese, or process
meat. If the whey protein-stabilized fatty emulsion of the
invention is used, the weight ratio of fatty emulsion to
foodstuff base is preferably in the range of from 20:80 to
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70:30. Similarly, if the acidified and heat-treated solution
of one or more whey proteins is used, the weight ratio of
whey proteins to foodstuff base is preferably in the range of
from 20:80 to 70:30. If a casein-containing foodstuff base is
used, the blending ratio of fatty emulsion or acidified whey
protein solution to casein-containing foodstuff base is
preferably such that the weight ratio of whey proteins to
casein in the resulting casein-containing foodstuff is in the
range of >10:90 to 80:20, more preferably 20:80 to 40:60. If
a meat protein-containing foodstuff base is used, the
blending ratio of fatty emulsion or acidified whey protein
solution to meat protein-containing foodstuff base is
preferably such that the weight ratio of whey proteins to
meat proteins in the resulting meat protein-containing
foodstuff is in the range of from 10:90 to 80:20, more
preferably 20:80 to 40:60. Especially, if meat proteins are
used, the resulting meat protein-containing foodstuff can
also include animal fat, such as beef tallow.
If desired, the resulting foodstuff may be further blended
and incubated with a transglutaminase enzyme. Normally, whey
proteins do not react with transglutaminases. The present
inventors have found that the pre-treatment of whey protein
solutions in the acid pH range (below the isoelectric pH of
the whey proteins) as described in this invention offers a
possibility to modify the behavior of whey proteins also
towards the action of transglutaminase. Accordingly, in
another aspect of the present invention, the process for
incorporating whey proteins into a foodstuff comprises the
further step of blending and incubating the resulting
foodstuff with the enzyme transglutaminase. As is generally
known by the person skilled in the art, there are different
transglutaminases, classified under the general nomenclature
EC 2.3.2.13, and any of these transglutaminases can be used
in the present invention. In particular, it is possible to
use a transglutaminase produced by Streptoverticilium
mobaraense which is commercially available under the name of
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"Aktiva-MP" from Ajinomoto. The enzyme employed is preferably
used in conventional amounts such as 1 to 6 u/g (units enzyme
per gram protein in the system). The incubating conditions
are preferably a temperature in the range of 20 to 60 °C,
more preferably 50 °C; a duration of 5 to 60 minutes; and a
pH of 5.5 to 7.5, more preferably 6 to 7. Preferably, no
shear is applied during the incubation period.
The foodstuff which is obtainable by the process according to
the invention, for example process cheese, cream cheese,
natural cheese, mayonnaise or process meat, is superior as
compared to foodstuffs of the prior art in that a high
firmness and short texture of the resultant products can be
accomplished even at high whey protein contents, which is not
observed when native whey proteins are utilized.
Specifically, if a casein-containing foodstuff is
manufactured, such as a process cheese formulation, high
protein to casein ratios of up to 80:20 by weight can be
established together with a favorable appearance and
excellent sensory properties.
Example 1
A whey protein concentrate (17.7 ~ total solids, 10
protein) with the majority of its proteins in their native
state is acidified with lactic acid down to pH 3.8.
Afterwards the acidified whey protein solution is blended
with 5 ~ molten butter at room temperature and homogenized at
220 bar and 60 °C. The emulsion is then heat treated at 85 °C
for 5 min. Then 34.2 parts of the heated emulsion are
immediately blended with 3.5 parts of rennet casein, 3.5
parts of milk concentrate, 1.4 parts of starch, 7 parts of
hard cheese, 15.9 parts of butter, 5.3 parts of whey powder,
3.0 parts of emulsifying salts, 1 part of salt and 25.2 parts
of water so as to complete 100 parts. After thoroughly
mixing, the blend is treated as in the conventional
manufacture of process cheese spreads.
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Example 2
A whey protein concentrate (17.7 $ total solids, 10
protein) with the majority of its proteins in their native
state is acidified with lactic acid down to pH 3.8.
Afterwards the acidified whey protein solution is blended
with 5 $ molten butter at room temperature and homogenized at
220 bar and 60 °C. The emulsion is then heat treated at 85 °C
for 5 min. Then 34.2 parts of the heated emulsion are
immediately blended with 3.5 parts of rennet casein, 3.5
parts of milk concentrate, 1.4 parts of starch, 7 parts of
hard cheese, 15.9 parts of butter, 5.3 parts of whey powder,
3.0 parts of emulsifying salts, 1 part of salt and 25.2 parts
of water so as to complete 100 parts. After thoroughly
mixing, the blend is incubated with a microbial
transglutaminase (5 units per gram protein in the blend) at
50 °C for 1 h. The blend is then treated as in the
conventional manufacture for process cheese spreads. The
following table shows the firmness (Stevens Texture Analyzer)
of the final cheese produced as described above compared to a
standard product and a product with a native whey protein
concentrate.
Product Whey protein: TransglutaminaseFirmness [g]
casein ratio
Standard 10:90 no 57
yes 160
With native 45:55 no 36
whey protein yes 64
With whey 45:55 no 42
protein yes 115
emulsion pH
3.8, heated
